Continuous neat polymerization and ambient grinding methods of polyolefin drag reducing agents

ABSTRACT

A process for continuously producing a polymer drag reducing agent (DRA) is described. The process concerns mixing a monomer and a catalyst in at least one continuously stirred tank reactor (CSTR) to form a mixture. The mixture is continuously injected into a volume continuously formed by a thermoplastic material, such as polyethylene. The thermoplastic material is periodically sealed off to form a temporary container or bag. The monomer is permitted to polymerize in the temporary container to form polymer. In one non-limiting embodiment, the polymerization in the bag takes place within an inert, circulating fluid that accelerates heat transfer. The polymer and the temporary container are then ground together, preferably at non-cryogenic temperatures, to produce a particulate polymer drag reducing agent. In one preferred, non-limiting embodiment, the grinding or pulverizing occurs in the presence of at least one solid organic grinding aid. Finally, the particulate polymer drag reducing agent may be combined with a dispersing fluid.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of U.S. patent applicationSer. No. 10/321,762 filed Dec. 17, 2002, now U.S. Pat. No. 6,649,670.

FIELD OF THE INVENTION

The invention relates to processes for producing polymeric drag reducingagents, and most particularly to processes for continuously producingpolymeric drag reducing agents in a finely divided particulate form athigh conversions.

BACKGROUND OF THE INVENTION

The use of polyalpha-olefins or copolymers thereof to reduce the drag ofa hydrocarbon flowing through a conduit, and hence the energyrequirements for such fluid hydrocarbon transportation, is well known.These drag reducing agents or DRAs have taken various forms in the past,including slurries or dispersions of ground polymers to formfree-flowing and pumpable mixtures in liquid media. A problem generallyexperienced with simply grinding the polyalpha-olefins (PAOs) is thatthe particles will “cold flow” or stick together after the passage oftime, thus making it impossible to place the PAO in the hydrocarbonwhere drag is to be reduced, in a form of suitable surface area, andthus particle size, that will dissolve or otherwise mix with thehydrocarbon in an efficient manner. Further, the grinding process ormechanical work employed in size reduction tends to degrade the polymer,thereby reducing the drag reduction efficiency of the polymer.

One common solution to preventing cold flow is to coat the groundpolymer particles with an anti-agglomerating or partitioning agent.Cryogenic grinding of the polymers to produce the particles prior to orsimultaneously with coating with an anti-agglomerating agent has alsobeen used. However, some powdered or particulate DRA slurries requirespecial equipment for preparation, storage and injection into a conduitto ensure that the DRA is completely dissolved in the hydrocarbonstream. The formulation science that provides a dispersion of suitablestability such that it will remain in a pumpable form necessitates thisspecial equipment.

Gel or solution DRAs (those polymers essentially being in a viscoussolution with hydrocarbon solvent) have also been tried in the past.However, these drag reducing gels also demand specialized injectionequipment, as well as pressurized delivery systems. The gels or thesolution DRAs are stable and have a defined set of conditions that haveto be met by mechanical equipment to pump them, including, but notnecessarily limited to viscosity, vapor pressure, undesirabledegradation due to shear, etc. The gel or solution DRAs are also limitedto about 10% polymer as a maximum concentration in a carrier fluid dueto the high solution viscosity of these DRAs. Thus, transportation costsof present DRAs are considerable, since up to about 90% of the volumebeing transported and handled is inert material.

U.S. Pat. No. 2,879,173 describes a process for preparing free-flowingpellets of polychloroprene involving suspending drops of an aqueousdispersion of the polychloroprene in a volatile, water-immiscibleorganic liquid in which the polymer is insoluble at temperatures below−20° C. until the drops are completely frozen and the polychloroprenecoagulated, separating the frozen pellets from the suspending liquid,coating them while still frozen with from 5% to 20% of their dry weightof a powder which does not react with the polychloroprene under normalatmospheric conditions, and removing the water and any adhering organicliquid through vaporization by warming the pellets.

A method for coating pellets of a normally sticky thermoplastic bindermaterial by using a mixture of a minor proportion of a vinylchloride/vinyl acetate copolymer and a major proportion of a chlorinatedparaffin wax with powdered limestone or talc powder is described in U.S.Pat. No. 3,351,601.

U.S. Pat. No. 3,528,841 describes the use of microfine polyolefinpowders as parting agents to reduce the tackiness of polymer pellets,particularly vinyl acetate polymers and vinyl acetate copolymers.

Similarly, Canadian patent 675,522 involves a process of comminutingelastomeric material for the production of small particles that includespresenting a large piece of elastomeric material to a comminutingdevice, feeding powdered resinous polyolefin into the device,comminuting the elastomeric material in the presence of the powderedpolyolefin and recovering substantially free-flowing comminutedelastomeric material.

A process for reducing oxidative degradation and cold flow of polymercrumb by immersing the crumb in a non-solvent such as water and/ordusting the crumb with a powder such as calcium carbonate and2,6-di-t-butylparacresol, 4,4′-methylene-bis-(2,6-di-t-butylphenol) orother antioxidants is discussed in U.S. Pat. No. 3,884,252. The patentalso mentions a process for reducing fluid flow friction loss inpipeline transmission of a hydrocarbon fluid by providing a continuoussource of the dissolved polymer.

U.S. Pat. No. 4,016,894 discloses that drag in turbulent aqueous streamsis reduced by a powder composition of a finely divided hygroscopic dragreducing powder, for example poly(ethylene oxide), and a colloidal sizehydrophobic powder, for example, an organo silicon modified colloidalsilica, and an inert filler such as sodium sulfate. The powdercomposition is injected into the turbulent stream by first mixing thepowder with water to form a slurry and immediately thereafter drawingthe slurry through an eductor into a recycle stream between thedownstream and upstream ends of a pump for the turbulent stream.

A polymer emulsification process comprising intimately dispersing aliquified water insoluble polymer phase in an aqueous liquid mediumphase containing at least one nonionic, anionic or cationic oil-in-waterfunctioning emulsifying agent, in the presence of a compound selectedfrom the group consisting of those hydrocarbons and hydrocarbylalcohols, ethers, alcohol esters, amines, halides and carboxylic acidesters which are inert, non-volatile, water insoluble, liquid andcontain a terminal aliphatic hydrocarbyl group of at least about 8carbon atoms, and mixtures thereof are described in U.S. Pat. No.4,177,177. The resulting crude emulsion is subjected to the action ofcomminuting forces sufficient to enable the production of an aqueousemulsion containing polymer particles averaging less than about 0.5microns in size.

U.S. Pat. No. 4,263,926 provides a method and apparatus for maintainingpolymer particles in readily recoverable, discrete form, and forinjecting the particles into a pipeline hydrocarbon by disposingparticulate polymer within a storage hopper having a cone bottom and anauger extending upwardly from the bottom. The auger is rotated to causethe polymer particles to revolve in the hopper, reversing the rotationof the auger to pass polymer particles downwardly into a mixing chamberbelow the hopper. The particles pass through a rotary metering valve, oroptionally, a bin activator, intermediate storage and rotary meteringvalve at the upper end of the chamber, simultaneously spraying a liquidsuch as oil or water tangentially in the chamber optionally agitatingthe chamber and removing a slurry of particulate polymer and liquid fromthe chamber and injecting the slurry into a pipeline hydrocarbon.

A technique for extremely rapid dissolution or dispersion on essentiallythe molecular level, of certain polymeric materials in compatible liquidvehicles is described in U.S. Pat. No. 4,340,076. The polymericmaterials are comminuted at cryogenic temperatures and are thenintroduced into a liquid vehicle preferably while still at or nearcryogenic temperatures. At low concentrations, the resulting blend orsystem displays reduced friction to flow while high concentrations maybe used to immobilize the liquid vehicle and/or reduce its vaporpressure.

From reviewing the many foregoing prior patents it can be appreciatedthat considerable resources have been spent on both chemical andphysical techniques for easily and effectively delivering drag reducingagents to the fluid that will have its drag or friction reduced. Yetnone of these prior methods has proven entirely satisfactory. Thus, itwould be desirable if a drag reducing agent could be developed whichrapidly dissolves in the flowing hydrocarbon (or other fluid), whichcould minimize or eliminate the need for special equipment forpreparation and incorporation into the hydrocarbon, and which could beformulated to contain greater than 10% polymer. It would also bedesirable to have a process for producing particulate drag reducingagents that did not require cryogenic grinding in its preparation and/oronly grinding under ambient temperature conditions.

Another important consideration in the production of polymeric dragreducing agents is the achieving of high conversions in thepolymerization reaction, which are defined herein as generally on theorder of at least 90%. High conversion makes the best use of the monomerand catalysts and achieves a high molecular weight polymer product. Thehigh molecular weight polymer product helps mitigate subsequentdegradation of the polymer product through size reduction, such asgranulation or grinding, as well as through shear when the DRA productpasses through pumps in the course of injecting it into a flowinghydrocarbon fluid or through a pipeline. Conventionally, highconversions and high molecular weights of DRA polyolefins are achievedby bulk or neat polymerizations conducted in batch reactions. However,it is well known in the art of polymerization science that the mostefficient method of producing polymers en masse is through the methodsof continuous polymerization processes. Thus, the preferred productionprocesses of high volumes of DRA product are continuous processes. Someprior efforts at the continuous production of DRA product by employingbulk polymerization methods have been explored but have not provenentirely satisfactory either. One innovative approach is to conduct bulkpolymerization at high conversion in a microcapsule described in U.S.Pat. Nos. 6,126,872 and 6,160,036, both of which are incorporated byreference herein.

It would thus be additionally advantageous if a continuous processexisted for producing DRA polymer product at high conversions andmolecular weight, yet in a form that was easily deliverable to a flowinghydrocarbon stream.

SUMMARY OF THE INVENTION

An object of the invention is to provide a process for producing apolymer drag reducing agent continuously at high conversion and highmolecular weight.

Other objects of the invention include providing a polymer DRA ofsuitable small particle size and adequate surface area (for quickdissolution and dissipation in a flowing stream) that can be readily andcontinuously manufactured and that does not require cryogenictemperatures to be produced.

Another object of the invention is to continuously produce a polymer DRAat high conversion and high molecular weight that may be easilyintegrated into a process for producing a particulate or slurry DRAproduct.

In carrying out these and other objects of the invention, there isprovided, in one form, a method for producing a polymer drag reducingagent that involves first mixing a monomer and a catalyst in at leastone continuously stirred tank reactor (CSTR) to form a mixture. Themixture is then continuously injected into a volume that is continuouslyformed by a thermoplastic material. The thermoplastic material isperiodically sealed off into a temporary container. Next, the monomer ispermitted to polymerize under conditions of controlled temperature andinert atmosphere in the temporary container to form polymer. Theresultant polymer and the temporary container are then ground, thelatter typically removed by mechanical steps, to produce particulatepolymer drag reducing agent. The particulate polymer drag reducing agentmay then be combined with a dispersing fluid, such as to form a slurryor dispersion product.

DETAILED DESCRIPTION OF THE INVENTION

The invention involves the application of a continuous polymerizationmethod in combination with non-cryogenic grinding or size reductionmethods to produce polymeric drag reducing agents in a finely dividedparticulate form. More particularly, the continuous polymerizationmethod involves a “form, fill and seal” packaging process, and the finalformulation of dispersed polymer does not contain the traditionalaqueous or glycolic, polar dispersing medium, but rather a mixture ofhydrocarbons more compatible with and “friendly” to dissolution inpipeline components, e.g. a flowing hydrocarbon stream.

The polymerization apparatus may be composed of at least one or a seriesof continuous stirred tank reactors (CSTRs) where raw materials (e.g.monomers and catalysts) are continuously charged, allowed an appropriatedwell or residence time in the reactor system, such that an adequatemolecular weight or viscosity is obtained, and subsequently dischargedin a continuous fashion to a “form, fill and seal” packaging device.

It is the nature of the “form, fill and seal” apparatus to utilize acontinuous sheet of thermo-formable or thermoplastic material tofabricate a container of some set or predetermined dimensions, performthe filling of said container by volumetric injection, and lastly sealthe container such that a self-contained bag or temporary container ofmaterial (in this case, catalysts and activated monomer), isperiodically or regularly captured in a continuous process.

In the “form, fill and seal” packaging device”, the “living” polymer,having achieved a suitable viscosity and/or molecular weight in theCSTR, is discharged into continuously formed volumes formed by thethermoplastic material, in one non-limiting embodiment, continuouslyformed low density polyethylene bags, thermally sealed, and dischargedto a collection point. The polyethylene bags, having been filled withthe catalyst and activated monomer mixture within an inert atmosphere,now serve as temporary and isolated reactor vessels or polymerizationsites. These temporary containers or reactor vessels are collected andkept again in the presence of an inert atmosphere, since thethermoplastic material is generally not designed to prevent thediffusion of contaminants such as oxygen, and allowed to polymerize tohigh conversion, e.g. at least 90% in one non-limiting embodiment. Inanother non-limiting embodiment of the invention, “high conversion” isconsidered to be at least 70%, dependent upon the amount of yield orrather the plasticized monomer one wishes to incorporate in an effort toaffect the overall dissolution of polymer particles. The completedpolymer is subsequently collected for grinding via ambient conditions.

The nature of the grinding process is such that a unique grinding aidrenders a granulated polyolefin polymer into a ground state of fineparticles of 600 microns or less at ambient conditions, in onenon-limiting embodiment of the invention. This size reduction processmay involve the use of an attrition mill, such as a Pallmann Pulverizer,in combination with a grinding aid or agent of suitable hardness in thatshearing and surface blocking properties are imparted into the grindingchamber such that particle agglomeration and gel ball formation of softpolyolefins is prevented.

In one non-limiting embodiment, the grinding aid may be amicrocrystalline component, such as a microcrystalline polymer orcopolymer. These solid grinding aids may be products such as MICROTHENE®ethylene-co-butylene crystalline powders available from Equistar. It hasbeen discovered that other, more traditional grinding aids such ascalcium stearate or ethylene-bis-stearamide are too soft and inadequatein preventing agglomeration of polymer in the grinding chamber. It isimportant that the solid grinding aid impart the required shearingaction in the grinding or pulverizing chamber in order to achieve thesmall polymer particles of 600 microns or less.

Another important portion of the invention is the formulation of thefinely ground, polymer drag reducing agents into suitable dispersingfluids such that the agent may be delivered in accurate concentrationsinto a pipeline, and at the same time, avoid the traditional unstabledispersive mixtures of the past. The literature is filled with examplesof slurries of drag reducing agents being composed of a variety ofmixtures, more commonly those of water and glycol mixtures, which tendto invariably suffer from cold flow problems.

The present invention avoids cold flow problems by providing for aunique slurry or non-solvent mixture based on a combination of severalhydrocarbon fluids in combination with one of those components having amelting point above two other fluids in the mixture. It has been foundthat the DRAs of this invention, once ground to 600 microns or smaller,may be dispersed in a hydrocarbon mixture composed, in one non-limitingembodiment of 25% polymer, 22.5% butyl cellosolve, 22.5% hexanol, and40% mineral oil such as a Penreco petrolatum (Penreco Ultima, meltingpoint 130–135° F.; 54–57° C.). These components are added together abovethe melting point of the petrolatum (in one non-limiting embodiment,140° F.; 60° C.), and upon cooling, the stable mixture formed exists asa thick slurry that may be pumped quite freely with traditional methodsand equipment. The petrolatum, once congealed, acts as a flow orstabilizing aid for the particulate system.

The invention will now be further discussed in more particular detail.Generally, the polymer that is processed in the method of this inventionmay be any conventional or well known polymeric drag reducing agent(DRA) including, but not necessarily limited to, poly(alpha-olefin),polychloroprene, vinyl acetate polymers and copolymers, poly(alkyleneoxide) (PAO), and mixtures thereof and the like. In one embodiment ofthe invention, the monomer is any monomer which, when polymerized, formsa polymer suitable for use as a drag reducing agent (DRA). Such monomersare well known in the art and include, but are not necessarily limitedto, alpha-olefins, such as 1-hexene, 1-octene, 1-decene, 1-dodecene,1-tetra-decene, and the like; isobutylene; alkyl acrylates;alkylmethacrylates; alkyl styrene; and the like. Copolymers of thesemonomers may also make suitable drag reducing agents.

Polyalpha-olefins, which in one non-limiting embodiment are preferredherein, are polymerized from the monomers or comonomers by conventionaltechniques and will have molecular weights above 10 million.Polyalpha-olefins particularly suitable for the processes andcompositions of this invention include the FLO® family of PAO DRAs,including FLO® 1004, FLO® 1005, FLO® 1008, FLO® 1010, FLO® 1012, FLO®1020 and FLO® 1022 DRAs sold by Baker Pipeline Products, a division ofBaker Petrolite Corporation. These DRAs are used for hydrocarbonstreams.

The polymerization of certain monomers may be conducted by the inclusionof a catalyst into the monomer during or prior to inclusion of themonomer in at least one CSTR, in a non-limiting example. Any knownsuitable catalyst and/or co-catalyst may be used for the method of thisinvention as long as they sufficiently catalyze the reaction to asufficient extent to meet the objectives of inventive method.Metallocenes are useful catalysts for polymerizing some monomers. In thecase of alpha-olefins, polymerization may be conducted by the inclusionof a mixture of Ziegler-Natta catalyst and co-catalyst(s) into themonomer. Catalysts for the polymerization of alpha-olefins include, butare not necessarily limited to, powdered catalyst TiCl₃AA (aluminumactivated titanium trichloride); co-catalyst(s), diethyl-aluminumchloride (DEAC), and diethylaluminum ethoxide (DEALE); TEAL (triethylaluminum chloride), tri-methyl aluminum, tri-isobutyl aluminum, MAO(methylaluminoxane) and the like. Of course, it will be necessary tomatch the co-catalyst with the main catalyst, so that the catalyticactivity of the main catalyst is triggered only by the presence of aparticular co-catalyst or class thereof. All components (monomer,catalyst, and co-catalyst(s)) required for the monomer to convert tohigh polymer can be brought together in various different ways that arenot necessarily critical to the invention herein. In one non-limitingembodiment of the invention, it may be necessary or desirable to use aseries of CSTRs prior to injection of the live or catalyst-activatedpolymer mixture into the volume surrounded by the continuously formedthermoplastic material.

Care must be taken to avoid poisons for particular catalysts orpolymerizations. For example, if Ziegler-Natta catalysts are used topolymerize α-olefins, the presence of oxygen must be avoided since itdeactivates both anionic and cationic catalyst systems. Water, in anyquantities other than minute molecular quantities, is also a poison. Aspreviously mentioned, the use of low density polyethylene as thethermoplastic material that is continuously formed to provide the bagsor containers for the monomer/catalyst mixture does not prevent thediffusion of gaseous contaminants such as oxygen through the material topoison the catalyst. Thus, the temporary containers package (alsoreferred to as bags, pouches, tubes, etc.) should be placed into aninert environment, such as a box, vault or room containing an inert gasor fluid. Other suitable thermo-formable materials besides low densityPE include, but are not necessarily limited to, polypropylene,polyvinylidene chloride, polyvinyl chloride, and combinations thereof.

In one non-limiting embodiment of the invention, the temporarycontainers are placed in a tank or reservoir that has an inert gas or acirculating liquid bath where the liquid is inert to the bag barrierfilm and also assists in channeling the heat resulting from thepolymerization away from the temporary containers to thereby assist inthe high conversion of the monomer. Suitable heat transfer fluidsinclude, but are not necessarily limited to, glycols such as ethyleneglycol, propylene glycol, etc.; mixtures of glycols with water; ISOPAR™L isoparaffin available from ExxonMobil Chemical, kerosene, and thelike. In one non-limiting embodiment of the invention, the temporarycontainers are placed in a larger, refrigerated box or container or“reefer” where the refrigeration also assists in removing the heat ofpolymerization from the reaction.

Certain monomers may be polymerized by the use of UV radiation toinitiate reaction in place of or in addition to the use of catalystsand/or co-catalysts. In such a system, the thermoplastic material wouldhave to be transparent to the frequency of the radiation necessary toinitiate or encourage polymerization of the monomer in the temporarycontainer.

A particular advantage of the technique of this invention is that thepolymerization may be conducted entirely within the bag or temporarycontainer under relatively small-scale bulk polymerization conditions inthe absence of a solvent, or in the presence of only a relatively smallamount of solvent. Conventionally, production of the very high molecularweight polymers useful as DRAs necessarily is done at high dilutions ina suitable solvent. Removal of large amounts of solvent thus becomes anissue, since transportation of large amounts of ineffective solvent tothe site of drag reduction is an unnecessary expense. However, in theinventive continuous process, very little or no solvent is required, andthe polymerization reaction may be conducted within the temporarycontainer by conventional techniques. Very high molecular weight DRAsmay be produced, for example on the order of 10 million weight averagemolecular weight or more. If solvent is used, the solvent proportion isat most only about 0.5 weight percent of the total mixture of monomerand catalyst, preferably at most only about 1.0%. Suitable solvents forthe polymerization of alpha-olefins include, but are not necessarilylimited to, kerosene, paraffinic Isopar solvents, isopentane, and thelike.

The sealing of the thermoplastic material around the mixture of monomerand catalyst to form the temporary containers (small scale bulkreactors) would generally occur periodically and regularly since theprocess is continuous and the form, fill and seal apparatus isautomatic. However, it is not necessary that the temporary containers beuniform in size and shape. As might be expected, the temporarycontainers will be generally tubular in shape and have a circularcross-section, however, this shape is generally a function of thecommercially available form, fill and seal machinery and is not criticalto the practice of the invention. The length of the temporary containersmay be practically limited by the dimensions of the vault, reservoir,bath or reefer where they reside while the monomer is permitted tocomplete reaction to form the polymer.

Sealing the thermoplastic material is more directly dictated by whetherthe monomer mixture has reached a predetermined viscosity so as topermit effective cutting off of the mixture and sealing into the bags ortemporary containers. This viscosity should be sufficiently high topermit the form, fill and seal machinery to operate without troublesomeleaks or excess mixture fouling the equipment or process. In onenon-limiting embodiment of the invention the viscosity of the mixtureshould reach at least 100 cP, and preferably at least 500 cP.

Alternatively, or in addition to the viscosity threshold discussedabove, it may be necessary or desirable for the still-reacting polymer(“living” polymer) to reach a certain minimum molecular weight before itis desirable to seal the temporary containers or bags and transfer thecontainers or bags to an inert environment for continued reaction tocompletion. The predetermined or desired molecular weight is more likelyto vary with the particular polymer involved, as contrasted withviscosity, which may be an acceptable threshold for a variety ofpolymers. In one non-limiting embodiment for polyalpha-olefins, onemolecular weight threshold to be reached may be about 1000 weightaverage molecular weight, preferably about 5000.

For the method of this invention, the polymeric DRA is preferably ofsufficient structure (molecular weight) to exist as a neat solid whichwould lend itself to the pulverizing process, i.e. that of being shearedby mechanical forces to smaller particles. A DRA of a harder, solidnature (relatively higher glass transition temperature) thanpoly(alpha-olefin) would certainly work. A DRA of a relatively softernature (lower glass transition temperature, more rubbery polymer) wouldbe more difficult to pulverize by processes to be described. A DRA thatexists as dissolved in solution (gel polymers) would have noapplicability here, of course.

A process has been discovered by which attrition mill pulverizingtechnology can be utilized in combination with unique grinding aids torender a granulated polyolefin polymer into a ground state of fineparticles of 600 microns or less at non-cryogenic conditions. Theprocess preferably involves the introduction of organic solid grindingaid into the grinding chamber such that particle agglomeration and gelball formation of soft polyolefins is minimized or prevented. The solidgrinding aid is also required to provide the shearing action necessaryin the grinding or pulverizing chamber to achieve the small polymerparticles of about 600 microns or less.

In one non-limiting embodiment of this invention, the grinding forproducing particulate polymer drag reducing agent is conducted atnon-cryogenic temperatures. For the purposes of this invention,cryogenic temperature is defined as the glass transition temperature(T_(g)) of the particular polymer having its size reduced or beingground, or below that temperature. It will be appreciated that T_(g)will vary with the specific polymer being ground. Typically, T_(g)ranges between about −10° C. and about −100° C. (about 14° F. and about−148° F.), in one non-limiting embodiment. In another non-limitingembodiment of the invention, the grinding for producing particulatepolymer drag reducing agent is conducted at ambient temperature. For thepurposes of this invention, ambient temperature conditions are definedas between about 20–25° C. (about 68–77° F.). In another non-limitingembodiment of the invention, ambient temperature is defined as thetemperature at which grinding occurs without any added cooling. Becauseheat is generated in the grinding process, “ambient temperature” may insome contexts mean a temperature greater than about 20–25° C. (about68–77° F.)—a typical range for the term “ambient temperature”. In stillanother non-limiting embodiment of the invention, the grinding toproduce particulate polymer drag reducing agent is conducted at achilled temperature that is less than ambient temperature, but that isgreater than cryogenic temperature for the specific polymer beingground. A preferred chilled temperature may range from about −7 to about2° C. (about 20 to about 35° F.).

Poly(alpha-olefin) is a preferred polymer in one non-limiting embodimentof the invention. As noted, poly(alpha-olefins) (PAOs) are useful toreduce drag and friction losses in flowing hydrocarbon pipelines andconduits. In one not limiting embodiment of the invention, the polymer,together with the thermoplastic material on the boundary of thetemporary container may have its size reduced in one step, or may haveits size reduced in multiple steps or stages. For instance, the polymermay be granulated, that is, broken up or otherwise fragmented intogranules in the range of about 6 mm to about 20 mm, preferably fromabout 8 mm to about 12 mm. It is permissible for the granulated polymerto have an anti-agglomeration agent thereon. Such agglomeration agentsinclude, but are not necessarily limited to talc, alumina, calciumstearate, ethylene bis-stearamide and mixtures thereof.

Within the context of this invention, the term “granulate” refers to anysize reduction process that produces a product that is relatively largerthan that produced by grinding. Further within the context of thisinvention, “grinding” refers to a size reduction process that gives aproduct relatively smaller than that produced by “granulation”.“Grinding” may refer to any milling, pulverization, attrition, or othersize reduction that results in particulate polymer drag reducing agentsof the size and type that are the goal of the invention.

While grinding mills, particularly attrition mills such as Pallmannattrition mills, Munson centrifugal impact mills, Palmer mechanicalreclamation mills, etc. may be used in various non-limiting embodimentsof the invention, other grinding machines may be used in the method ofthis invention as long as the stated goals are achieved.

The solid organic grinding aid may be any finely divided particulate orpowder that inhibits, discourages or prevents particle agglomerationand/or gel ball formation during grinding. The solid organic grindingaid may also function to provide the shearing action necessary in thepulverizing or grinding step to achieve polymer particles of the desiredsize. The solid organic grinding aid itself has a particle size, whichin one non-limiting embodiment of the invention ranges from about 1 toabout 50 microns, preferably from about 10 to about 50 microns. Suitablesolid organic grinding aids include, but are not necessarily limited to,ethene/butene copolymer (such as MICROTHENE®, available from Equistar,Houston), paraffin waxes (such as those produced by Baker Petrolite),solid, high molecular weight alcohols (such as Unilin alcohols (C12–C60)available from Baker Petrolite), and any non-metallic, solid compoundscomposed of C and H, and optionally N and/or S which can be prepared inparticle sizes of 10–50 microns suitable for this process, and mixturesthereof. As previously mentioned, some traditional grinding aids such astalc, calcium stearate, ethylene-bis-stearamide were discovered to beineffective as solid, organic grinding aids. In one particular,non-limiting embodiment, the solid organic grinding aid of thisinvention has an absence of fatty acid waxes.

It will be appreciated that there will be a number of different specificways in which the invention may be practiced that are within the scopeof the invention, but that are not specifically described herein. Forinstance, in one non-limiting embodiment of the invention, a granulatedpolymer is fed into the grinding chamber at a rate of from about 100 toabout 300 lbs/hr (45–136 kg/hr) and the solid organic grinding aid isfed at a rate of from about 10 to about 90 lb/hr (4.5–41 kg/hr).Preferably, a granulated polymer is fed into the grinding chamber at arate of from about 200 to about 300 lb/hr (91–136 kg/hr) and the solidorganic grinding aid is fed at a rate of from about 10 to about 30 lb/hr(4.5–14 kg/hr). As noted, all of the components may be fedsimultaneously to the grinding chamber. Alternatively, the componentsmay be mixed together prior to being fed to the grinding chamber. Inanother non-limiting embodiment of the invention, the components areadded sequentially, in no particular order or sequence. Grinding speedsof 3600 rpm utilized in a Pallmann PKM model and 5000 rpm utilized in aUniversal mill were found to be acceptable in specific, non-limitingembodiments of the invention.

In one non-limiting embodiment of the invention, it is expected that theprocesses described herein will produce particulate polymer dragreducing agent product where the average particle size is less thanabout 600 microns, preferably where at least 90 wt % of the particleshave a size of less than about 600 microns or less, 100 wt. percent ofthe particles have a size of 500 microns or less, and most preferably61.2 wt. % of the particles have a size of 297 microns or less innon-limiting embodiments. One achievable distribution is shown in TableI utilizing a PKM-600 model grinder; a series of other particledistributions vs. the screen size is displayed in Table II with theUniversal Mill.

TABLE I Micron Retained Screen Mesh Size Percent 500 35 38.8 g  297 5055.7 g  210 70 4.1 g 178 80 0.4 g 150 100 0.4 g pan pan 0.6 g

TABLE II Particle Size (microns) 35 Mesh Screen 30 Mesh Screen 20 MeshScreen 800 5 2 2 700 600 17 500 4 11 18 400 35 27 20 200 35 32 24 10014/7 16/12 11/8

In one non-limiting embodiment of the invention, during the grindingstage (and/or the granulation stage, if any) any excess solid grindingaid and at least a portion of the temporary container are removed fromthe grinding (and/or granulation) process. This removal may be conductedby any suitable conventional or future process including, but notnecessarily limited to, vacuum, cyclone, centrifugation, etc.

One useful device that has been utilized to remove bag material is the“multi-aspirator” produced by Kice Industries. A successful separationstrial of granulated polymer (C6/C12 bulk polymer) and PE sheeting wasperformed at Kice Industries facilities in Wichita, Kans. The trial wasconducted on a model 6F6 “multi-aspirator” unit utilizing consecutiveincreased air volumes, combined with a static de-ionizing bar, toessentially remove all of the free PE sheet mixed with the granulatedpolymer. Once ideal conditions were determined for separation, a drum ofthe granulated was run through the “multi-aspirator” for furthertesting.

If a suitable thermoplastic or thermo-formable material is selected forthe form, fill and seal process, then it is permissible or acceptablefor small quantities of this material to be retained with the polymerproduct. In one non-limiting embodiment of the invention, approximately0.05 wt. % or less of the thermoplastic material, and approximately 35wt. % or less of the grinding aid may be permitted in the resultantparticulate polymer drag reducing agent. However, residual bag materialis typically filtered out by Sweko filtration prior to material going tothe field.

In one preferred embodiment of the invention, the finely ground, dragreducing agents are dispersed in a suitable fluid as previouslymentioned. The dispersing fluid is preferably a mixture of at least twohydrocarbon fluids, where a first fluid has a melting point above themelting point of a second fluid. In another preferred embodiment of theinvention, the dispersing fluid includes at least three hydrocarbonfluids, where one of the fluids has a melting point above the meltingpoints of the other two fluids.

In the case where two components are used in the dispersing fluid, thefirst fluid may range from about 30 wt % to about 35 wt % of the totaldispersing fluid, and the second fluid may range from about 40 wt % toabout 45 wt % of the total dispersing fluid. In the case where thedispersing fluid is composed of at least three components, the firstfluid may range from about 30 wt % to about 35 wt % of the totaldispersing fluid, and the combined proportion of the other two componentfluids (or multiple components) may range from about 40 wt % to about 45wt % of the total dispersing fluid.

In one non-limiting embodiment of the invention, from about 25 to about30 weight % of the total slurry is the polymer DRA of the invention,preferably from about 28 to about 32 weight % of the total slurry.

It is critical when dispersing the polymer into a fluid mixturecontaining an ambient solid petroleum compound, that the fluid mixturebe heated above the melting point of the petroleum oil. Once mixed andallowed to cool, moderate agitation is utilized to render a flowablemixture. (There is no particular or critical method or technique forincorporating the ground DRA polymer into the dispersing fluid, as longas the slurry is mixed or combined to be uniform.) A surprising featureof the dispersing fluid aspect of the invention is that no additionalemulsifiers, dispersants, surfactants and/or thickening agents arerequired to keep the particulate polymer DRA stable in the slurry, as isoften the case with prior DRA slurries.

It is expected that the resulting particulate polymer DRAs can be easilytransported without the need for including appreciable amounts of aninert solvent, and that the particulate polymer DRAs can be readilyinserted into and incorporated within a flowing hydrocarbon, andpossibly some oil-in-water emulsions or water-in-oil emulsions, asappropriate. DRA products made by the process of this invention flowreadily under moderate pressure or pumping and contain a relatively highpercentage, from about 70–80% of active polymer. Furthermore, there isan absence of any need to add an additional anti-agglomeration aid orpartitioning agent to the DRA after it is ground to its desirable size.After the polymer is ground, a concentrated mixture of 70–80% polymermixed with grinding aid results. Once the polymer is placed in thedispersing fluids, the amount of polymer averages about 25–30% in thedispersive mixture.

In another non-limiting embodiment of the invention, the thermoplasticmaterial (such as polyethylene) into which the polymerizing mixture isinjected, and which material forms the temporary container, is replacedby a polar solvent-soluble thermosealing material, such as polyvinylalcohol. The thermosealing materials would serve essentially the samepurpose as the thermoplastic material. The thermosealing materials wouldbe similar to the thermoplastic materials and have the same or similarbarrier properties with respect to heat transfer fluids in that theywould be impenetrable. Each thermosealing material would also be similarin its ability to be cut and thermally sealed to itself to form thetemporary container. In one non-limiting embodiment of the invention,the thermosealing materials may be sealed at a temperature between about120 and about 150° C.

However, the thermosealing materials would have different solubilityproperties from the thermoplastic materials such as polyethylene in thatthey would be soluble in polar solvents. This difference in propertywould significantly alter the method by which the bag or temporarycontainer is separated from the final DRA polymer product. Instead ofmechanically removing the container, the DRA polymer and encapsulatingtemporary container may be placed in a polar solvent, with or withoutagitation, thus dissolving the bag entirely. Alternatively, the polarsolvent may be sprayed or otherwise applied to the thermosealingmaterial container to remove it. Upon dissolving the thermosealingmaterial from the surface of the DRA polymer, the DRA polymer iscollected to be further granulated and ground as described in thisinvention. The solution of the thermosealing material in the solvent maybe collected as a waste stream, or as a potential dispersing aid in afinal formulation containing the DRA polymer and dispersing fluid aswill be further explained.

Acceptable polar solvent-soluble thermosealing materials include, butare not necessarily limited to polyvinyl alcohol (PVA) and variousgrades of polyvinyl acetate having differing amounts of OH functionalityvia hydrolysis. By the phrase “polyvinyl acetate having at least somehydroxyl functionality” is meant polyvinyl acetate that has beenhydrolyzed so that the polymer chains have an average of one hydroxylgroup per chain. Suitable polar solvents include, but are notnecessarily limited to water, ethylene glycol, propylene glycol,diethylene glycol, dipropylene glycol, isopropyl alcohol, butyl alcohol,dipropylene glycol methyl ether, and mixtures thereof.

Yet another alternative, non-limiting embodiment of the inventioninvolves the utilization of the thermosealing material dissolved in thepolar solvent as a process fluid. That is, the process fluid would becomposed of solubilized PVA and one or more of the above-mentionedprocessing solvents. The DRA polymer (at least already partially ground)would be combined with the process fluid and ground further to produce aDRA dispersion. Thus, in one non-limiting embodiment it may beadvantageous to dissolve the PVA bag material in glycolic solvents orglycolic/water mixtures and utilize these same solutions of PVA forfinal processing of granulated DRA in a last stage grinder. In essence,granulated DRA polymer may be added to recaptured PVA processing fluidand this mixture subsequently utilized for final product dispersion orformulation purposes.

In another non-limiting embodiment of the invention, the PVA dispersionin polar solvent may be used as a process fluid in any size reductionoperation, including but not necessarily limited to, the granulation orinitial grinding of the DRA polymer. In the case of using the dispersionas a process fluid for initial granulation, the same process fluid couldbe used in subsequent grinding to reach the 250–500 micron particlesize. It will be appreciated that generally the term “grinding” is usedherein to mean any size reduction using physical (as contrasted withchemical) operations. Often grinding is done in multiple steps to reduceitems to ever smaller sizes. Occasionally, the term “granulation” isused to refer to an initial size reduction. It should be appreciatedthat the invention is not limited to any particular size of temporarycontainers.

Polyvinyl alcohol polymers (more precisely, polyvinyl acetate polymerhydrolyzed to hydroxyl functionality) are more typically utilized asstabilizing aids in suspension polymerization technology and in aqueousdispersion technology. Although PVA is unable to form micellularstructures in aqueous medium due to its polymeric structure, suspensionbehavior is well documented for PVA. Polyvinyl alcohol cannot bepolymerized directly from vinyl alcohol due to an abundance offree-radical transfer. Thus, polyvinyl acetate is prepared andhydrolyzed via a hydrolytic reaction to various degrees of hydroxylfunctionality. This degree of hydrolysis also gives the polymer chemistthe ability to adjust the degree of solubility to aqueous oraqueous/glycolic solvents. Hence, the degree of water solubility desiredcan be adjusted per the process.

The invention will now be further described with respect to specificexamples that are provided only to further illustrate the invention andnot limit it in any way.

EXAMPLE 1

Polymerization

An upgraded pilot operation for the production of neat or bulk polymerusing a 30-liter Buss reactor included three areas of activity. Theyencompass at least (a) a polymerization operation comprised of a halfgallon (1.9 liter) CSTR vessel, the accompanying Buss reactor andassociated monomer/catalysts pumps, and sieve bed systems, (b) apackaging operation, i.e. a “form, fill, and seal” packaging machinewith an enclosure as assembled by J&J Manufacturing, and (c) a recoveryoperation whereby 16-inch long (41-cm) polyethylene bags filled withactivated monomer were to be captured and placed in a nitrogen purged,refrigerated area for further polymerization.

Thus, the polymerization apparatus was composed of two CSTRs (continuousstirred tank reactors) whereby raw materials (monomers and catalysts)were continuously charged, allowed an appropriate dwell or residencetime in the reactor system such that an adequate molecular weight orviscosity is obtained, and subsequently discharged in continuous fashionto the form, fill, and seal packaging apparatus. In the packagingapparatus, the “living” polymer (having achieved a suitable viscosity)is discharged into low density polyethylene bags, the bags beingcontinuously formed by thermoplastic techniques and thereafter, chargedwith activated polymer mixture (flowing from the CSTR), thermallysealed, and discharged to a collection point. The polyethylene bags,having been filled with catalyst, activated monomer mixture and nowserving as isolated reactor vessels or polymerization sites, arecollected, kept in the presence of an inert atmosphere (since the bagsare not designed to prevent the diffusion of contaminants such asoxygen), allowed to polymerize to high conversion (approximately 90%),and the polymer subsequently collected for grinding.

As stated above, both monomers and catalysts were charged to the initialCSTR, where adequate mixing took place, prior to the fluids entering theBuss reactor for enhanced residence or polymerization time with constantagitation. During time in the Buss reactor, suitable viscosity wasreached such that catalyst particles were actually suspended in thepolymerizing mixture. Within 10–15 minutes of mixing in the Bussreactor, the slightly viscous polymer mixture was pumped in continuousfashion into the charge line leading to the collection hopper atop the“form, fill, seal” apparatus. Thus, the hopper served as the finalreservoir as the product was fed into the volumetric charge system onthe packaging device, in essence, charging 1 lb (0.45 kg) of productinto a polyethylene formed bag every 30 seconds. In subsequent fashion,the filled bags were collected and placed in two (nitrogen purged)refrigeration boxes and left to polymerize for 24 hours. During the timein the polymerization box, the polymer reached an estimated 55–65%solids. Upon retrieval from the cold boxes, the polymer bags containingneat polymer were quickly transferred to drums, blown down with nitrogenand transported to a refrigerated trailer where polymerization continuedover a 4–6 day period. Conversions on the order of 90% were reached inthis time (which is also a function of catalyst concentration andtemperature).

Form, Fill, and Seal (FFS) Packaging

The “form, fill, and seal” packaging device as assembled by J&JManufacturing, was not traditionally utilized for Class I, Division Ienvironments. Thus, the machine was modified with an enclosure in whichpositive nitrogen pressure could be maintained in order to meet the NFPA496 standard for purged and pressurized enclosures for electricalequipment. The enclosure was retro-fitted with a purge panel in order tomaintain positive nitrogen pressure for safe operation of the packagingmachine. Doorways to the enclosure were also fitted with devices todetect opening of the doors such that power could be immediately shutdown. As a secondary and independent sensing device, an oxygen sensorwas also installed in the enclosure that allowed one to manually monitorthe oxygen levels in the box. An alarm module was thus set to trip whenoxygen levels are too high, also cutting off power to the packagingdevice. Ziegler-Natta polymerization of polyolefins can be quite oxygensensitive, thus the maintenance of a pristine environment with respectto the lack of oxygen can be vital for success as well as safety.

In order to maintain cooling across the reactor and FFS device, thecharge line from the Buss reactor to the hopper sitting atop thepackaging machine was insulated with polyurethane insulation. The hopperwas also modified with a cooling jacket and plumbed into theglycol/water coolant line. During bagging operations, the hoppertemperature was held at 12° C. A nitrogen purge was also connected tothe hopper along with a 3-way valve on the charge line such that reactorflows could be diverted to a collection area if necessary. The samepathway can be utilized to wash the reactor charge line system withIsopar C for cleaning purposes at the end of a production run.

During normal operations of the packaging machine, polyethylene (PE)sheeting (7 inches (18 cm) wide) was pulled down over a cylindricalforming collar and the PE heat sealed into a 3 inch (7.6 cm) diametertube. The sealing temperatures on the various surfaces averaged 295° F.(146° C.). Once the bottom and rib of the 16 inch (41 cm) long PE bagwere thermally sealed, the filling operation took place such that 1pound (45 g) of activated monomer was delivered to the bag. The filledbag was then advanced downwards and jaws will cut and thermally sealedthe upper portion of the bag. The bag subsequently dropped down into thecatch or holding tube to await another filling cycle. The two gatevalves arranged on the drop tube system were aligned with signalsassociated with the filling device and the jaw closing sequence, thusthe same opening/closing sequence allowed the capture, holding, andeventual depositing of the bag out of the bottom of enclosure, and atthe same time, maintained integrity of the positive nitrogen pressure.The packaging apparatus deposited 2 bags per minute or 2 lbs (908 g) ofpolymer per minute, which equaled the proposed continuous 120 lb (54 kg)an hour charge rate into the Buss reactor.

Bag Recovery/Polymerization Box/Reefer Storage

Monomer filled bags were captured from below the packaging apparatus atthe rate of 2 bags per minute. Bags were collected for several minutesin a cold ice chest vented with nitrogen prior to making the manual tripto the refrigeration box for further polymerization. The polymerizationbox was fitted with rubber glove inserts, drop tube assemblies, as wellas an array of baskets (60 per box) and a rack system to facilitate theplacement and storage of bags. Catch pans were also situated in thebottom of the boxes to catch any leaking polymer. One of the uniquefeatures discovered about the neat or bulk FLO polymer is that leakstended to be self-sealing. Thus, as the polymerization proceeds in thestatic environment of the bag, the viscosity increases and actuallyseals off the area of leakage. Polymerization boxes were also purgedwith nitrogen and the temperature was set at 22° F. (−5.6° C.).

Bags were held in the cold polymerization boxes for at least 24 hours aspolymer conversion approached 55–65%. At such time the bags of polymerwere quickly unloaded from the boxes into drums fitted with nitrogensparing systems. After nitrogen sparing of the drums, they were cappedand again moved quickly to the refrigerated trailer near the generatorsystem. The product spent approximately 4–6 days achieving conversionsof 85–90% in the 35–40° F. (1.7–4.4° C.) environment. Oncepolymerization was complete, the PE was removed from the polymer inmanual fashion and the polymer moved to the granulating unit for sizereduction.

EXAMPLE 2 Reaction 1644-137

Prior to the installation of the form, fill, seal device, experiment1644-137 was run to demonstrate the feasibility/applicability ofcontinuously charging the reactor system with monomer and catalyst.Thus, the material of this Example was transferred over to arefrigeration box into lay-flat tubing in order to allow for a completepolymerization or conversion to high polymer solids. Lay-flat tubing inthis case is described as a continuous length of low densitypolyethylene tubing (4 mils thick) situated in the refrigeration box,connected to the Buss reactor via charge line, and blown down withnitrogen to provide an inert atmosphere. Thus, the Buss reactor was runfor several hours at an alpha-olefin monomer charge rate of 90 lbs./hour(41 kg/hr), with the polymer outflow being transferred into the lay-flattubing upon each reactor filling cycle. This particular reaction was runat what was thought to be a relatively high catalyst level andsurprisingly high drag reduction values were obtained after 24 hours ofreaction time. Upon capturing the polymer after the 24-hour reactioncycle, the material was stored under nitrogen in the refrigerationtrailer at 35–37 F. (1.7–2.80° C). The final % drag or % solids at finalconversion was not determined. In one non-limiting embodiment of theinvention, one goal is to achieve % drag reduction in the range of60–55% at 0.25 ppm active polymer in the hydrocarbon stream beingtreated. Results are shown in Table III.

TABLE III Solids and Drag Reduction Achieved for Reaction Example 2 CoreOuter Sample Sample Core % Drag/Outer Reaction Example 2 Solids SolidsDrag at 0.25 PPM Time/Temp. Lay-flat 57.9% 52.3% 52.8/48.3 24 hr atTubing #1 18–25° F. (−7.8– −3.9° C.) Lay-flat 63.8% 48.1% 59.2/56.4 24hr at Tubing #2 18–25° F. (−7.8– −3.9° C.)

Subsequent to the Examples discussed above, it was discovered thatholding the bags or temporary containers of polymerizing polymer in coldpolymerization boxes was manually intensive and did not provide theideal heat transfer for the reaction. Thus, permitting the monomer topolymerize in the temporary containers or bags in an inert liquid and/orinert environment where the liquid was circulated greatly improved heattransfer and assisted in optimizing the polymerization reaction. Storingthe temporary containers in Isopar L or a propylene glycol/water (PG)mixture was found suitable. The ratio of propylene glycol/water in thePG mixture was 60 wt % to about 40 wt %, although it will be appreciatedthat other ratios and other glycols may also find use as suitablecirculating and heat transfer fluids.

Further details about grinding and size reduction of the polymerproduced in the method of this invention to give a particulate polymerDRA prior to introduction into a hydrocarbon fluid may be found in U.S.patent application Ser. No. 10/322,050, filed herewith, incorporated byreference herein.

EXAMPLE 3 Reaction 1644-163

A successful “continuous bulk polymerization/bagging/capture” experimentwas performed using similar conditions as in Example 2, however, in thiscase the polymer outflow was transferred directly to the form, fill,seal apparatus where continuous bagging took place. It was againrealized early in the run that initial catalyst levels were too high.These catalysts levels were eventually reduced from a high to low rangeover the one and one half hour course of the reaction/bagging exercise.Altogether, over 150 lbs (68 kg) of bagged polymer was collected.Instead of storing the captured bags in a under nitrogen in arefrigeration trailer, these bags were stored in drums of cold fluidsuch as kerosene and Isopar L. Nitrogen was bubbled through the drums offluid to achieve adequate mixing and heat dispersion. Conversions anddrag efficiencies were measured after 48 hours and found to be 76%solids and 57% drag at 0.25 ppm polymer concentration.

EXAMPLE 4 Reaction 1644-181

Successful “continuous bulk polymerization/bagging/capture” experimentswere also conducted with increased monomer rates. In this particularexample, a total monomer composition rate of 200 lbs (91 kg) an hourcoupled with an appropriate catalyst/co-catalyst concentration wasutilized during the two hour experiment. Thus, the outflow from the Bussreactor was discharged to the form, fill, seal, device where the baggingrate was adjusted to four bags per minute. Bags collected were stored ina basket fitted to 330 gallon (1.2 m³) totes filled with cold kerosene(26° F.; −3° C.); the totes were bubbled with nitrogen to improve heattransfer.

The basket containing the bagged polymer was removed from the kerosenetote after 24 hours and transferred to a second tote in a refrigeratedtrailer. This second tote contained propylene glycol held at 38° F. (3°C.). The polymer was allowed to continue the conversion process forseveral days submerged in the propylene glycol whereupon conversion wasmeasured as 76% solids and the drag efficiency measured as 53% at 0.25ppm polymer concentration.

EXAMPLE 5

A 250 gallon (0.95 m³) stainless steel tote was fitted with side heatingelements such that the tote and contents could be heated to at least140° F. (60° C.). The tote was subsequently charged with 180 lbs (82 kg)hexanol and 180 lbs (82 kg) of butyl cellosolve. While the tote heatedovernight, a drum of Penreco Ultima (melting point 130–135° F., 54–57°C.) was rendered into its molten state with an overnight stay in theappropriate hot-box. Once the tote and its contents reached 140° F. (60°C.), the Penreco Ultima was retrieved from the hot-box and quickly addedto the tote with stirring from a lightening mixer and re-circulationutilizing an air pump. Immediately upon mixing the mixture was allowedto cool with continued moderate mixing. The resulting composition was apasty slurry having a viscosity of 300–400 cP.

Many modifications may be made in the composition and process of thisinvention without departing from the spirit and scope thereof that aredefined only in the appended claims. For example, the exact nature ofand proportions of monomer and catalyst, solid organic grinding aid, therate of production, the details of the form, fill and seal apparatus andmethod, the grinding process, the exact composition of the dispersingfluid etc. may be different from those used here. Particular processingtechniques may be developed to enable the components to be homogeneouslyblended and work together well, yet still be within the scope of theinvention. Additionally, feed rates of the various components areexpected to be optimized for each type of CSTR; form, fill and sealapparatus; grinding equipment and for each combination of particularcomponents employed.

1. A method for producing a polymer drag reducing agent, comprising:mixing a monomer and a catalyst in at least one continuously stirredtank reactor (CSTR) to form a mixture; continuously injecting themixture into a volume continuously formed by a polar solvent-solublethermosealing material; periodically sealing off the thermosealingmaterial into a temporary container; permitting the monomer topolymerize in the temporary container to form polymer; removing thetemporary container with a polar solvent; and grinding the polymer toproduce particulate polymer drag reducing agent.
 2. The method of claim1 where the polar solvent-soluble thermosealing material is selectedfrom the group consisting of polyvinyl alcohol and polyvinyl acetatehaving at least some hydroxyl functionality.
 3. The method of claim 1where the point at which the sealing off occurs to form the temporarycontainer is selected from the group consisting of (1) the mixturereaching a predetermined viscosity, (2) the polymer reaching apredetermined molecular weight, and (3) a combination of (1) and (2). 4.The method of claim 1 where in permitting the monomer to polymerize inthe temporary container, the container is placed in an inertenvironment.
 5. The method of claim 4 where the inert environment is abath of circulated fluid that removes heat of polymerization from thepolymer.
 6. The method of claim 1 where the grinding is conducted at atemperature above the glass transition temperature of the polymer. 7.The method of claim 1 where the grinding is conducted in the presence ofa grinding aid.
 8. The method of claim 7 where the grinding aid is asolid organic grinding aid having a size between about 1 and about 50microns.
 9. The method of claim 7 where the grinding aid is selectedfrom the group consisting of ethene/butene copolymer, paraffin waxes,solid alcohols, and mixtures thereof.
 10. The method of claim 1 where atleast some grinding of the polymer is conducted in the presence of aprocess fluid comprising the polar solvent having at least a portion ofthermosealing material dissolved therein.
 11. The method of claim 1further comprising combining the particulate polymer drag reducing agentwith a dispersing fluid to form a slurry product.
 12. The method ofclaim 11 where the dispersing fluid is a mixture of at least twohydrocarbon fluids comprising a first fluid having a melting point abovea melting point of a second fluid.
 13. The method of claim 12 where inthe dispersing fluid, the first fluid ranges from about 30 wt % to about35 wt % and the second fluid ranges from about 40 wt % to about 45 wt %based on the total volume of the dispersing fluid.
 14. The method ofclaim 12 where the polar solvent is selected from the group consistingof water, ethylene glycol, propylene glycol, diethylene glycol,dipropylene glycol, isopropyl alcohol, butyl alcohol, dipropylene glycolmethyl ether, and mixtures thereof.
 15. The method of claim 1 where inmixing the monomer and the catalyst, the monomer is an alpha-olefin. 16.The method of claim 1 where the particulate polymer drag reducing agenthas an average particle size of equal to or less than about 600 microns.17. The method of claim 1 where the grinding is conducted at ambienttemperatures.
 18. A method for producing a polymer drag reducing agent,comprising: mixing a monomer and a catalyst in at least one continuouslystirred tank reactor (CSTR) to form a mixture; continuously injectingthe mixture into a volume continuously formed by a polar solvent-solublethermosealing material; periodically sealing off the thermosealingmaterial into a temporary container; permitting the monomer topolymerize in the temporary container in an inert environment to formpolymer; removing the temporary container with a polar solvent; andgrinding the polymer at a temperature above the glass transitiontemperature of the polymer to produce particulate polymer drag reducingagent.
 19. The method of claim 18 where the polar solvent-solublethermosealing material is selected from the group consisting ofpolyvinyl alcohol and polyvinyl acetate having at least some hydroxylfunctionality.
 20. The method of claim 18 where the point at which thesealing off occurs to form the temporary container is selected from thegroup consisting of (1) the mixture reaching a predetermined viscosity,(2) the polymer reaching a predetermined molecular weight, and (3) acombination of (1) and (2).
 21. The method of claim 18 where in thepermitting the monomer to polymerize in the temporary container, theinert environment is a bath of circulated fluid that removes heat ofpolymerization from the polymer.
 22. The method of claim 18 where thegrinding is conducted in the presence of a grinding aid.
 23. The methodof claim 22 where the grinding aid is selected from the group consistingof ethene/butene copolymer, paraffin waxes, solid alcohols, and mixturesthereof.
 24. The method of claim 18 where at least some grinding of thepolymer is conducted in the presence of a process fluid comprising thepolar solvent having at least a portion of thermosealing materialdissolved therein.
 25. The method of claim 18 further comprisingcombining the particulate polymer drag reducing agent with a dispersingfluid to form a slurry product.
 26. The method of claim 25 where thedispersing fluid is a mixture of at least two hydrocarbon fluidscomprising a first fluid having a melting point above a melting point ofa second fluid.
 27. The method of claim 26 where in the dispersingfluid, the first fluid ranges from about 30 wt % to about 35 wt % andthe second fluid ranges from about 40 wt % to about 45 wt % based on thetotal volume of the dispersing fluid.
 28. The method of claim 18 wherethe particulate polymer drag reducing agent has an average particle sizeof equal to or less than about 600 microns.
 29. The method of claim 18where the polar solvent is selected from the group consisting of water,ethylene glycol, propylene glycol, diethylene glycol, dipropyleneglycol, isopropyl alcohol, butyl alcohol, dipropylene glycol methylether, and mixtures thereof.
 30. The method of claim 18 where thegrinding is conducted at ambient temperatures.
 31. A slurry ofparticulate polymer drag reducing agent comprising: a particulatepolymer drag reducing agent; and a process fluid, where the processfluid comprises: a polar solvent; and a polar solvent-solublethermosealing material dissolved in the polar solvent.
 32. The slurry ofclaim 31 where the polar solvent is selected from the group consistingof water, ethylene glycol, propylene glycol, diethylene glycol,dipropylene glycol, isopropyl alcohol, butyl alcohol, dipropylene glycolmethyl ether, and mixtures thereof.
 33. The slurry of claim 31 where thepolar solvent-soluble thermosealing material is selected from the groupconsisting of polyvinyl alcohol and polyvinyl acetate having at leastsome hydroxyl functionality.
 34. The slurry of claim 31 where theparticulate polymer drag reducing agent is polyalpha-olefin.
 35. Theslurry of claim 31 where the particulate polymer drag reducing agent hasan average particle size of equal to or less than about 600 microns. 36.The slurry of claim 31 further comprising a grinding aid.
 37. The slurryof claim 36 where the grinding aid is a solid organic grinding aidhaving a size between about 1 and about 50 microns.
 38. The slurry ofclaim 36 where the grinding aid is selected from the group consisting ofethene/butene copolymer, paraffin waxes, solid alcohols, and mixturesthereof.
 39. A slurry of particulate polymer drag reducing agentcomprising: a particulate polyalpha-olefin drag reducing agent having anaverage particle size of equal to or less than about 600 microns; and aprocess fluid, where the process fluid comprises: a polar solvent; and apolar solvent-soluble thermosealing material dissolved in the polarsolvent.